1. Field of the Invention
The present invention relates to a piercing apparatus suited for use as an iron runner port-opening machine for a blast furnace, or the like furnace, in an iron and steel factory.
2. Description of the Related Art
As an iron runner port-opening machine for a blast furnace, or the like furnace, in general, there has been widely used a hydraulic drifter having a cylinder for slidably holding a piston that moves back and forth, and a sleeve for holding a shank rod attached to a front portion of the cylinder, so that the piston is advanced by the hydraulic pressure supplied to the cylinder to blow the shank rod. A piercing rod is joined to an end of the shank rod, and a bit is attached to an end of the piercing rod to execute the piercing. During the piercing operation, a thrust is imparted to the drifter by a feed unit provided on a support unit that supports the drifter when the piercing is effected to a desired depth, the drifter is moved back to withdraw the piercing rod and the bit from the hole that is pierced. In this case, however, there frequently occurs an accident, i.e., a so-called jamming in which the bit is not easily withdrawn as the pierced hole is stuffed with the pulverized scraps on the back side of the bit.
In order to easily withdraw the bit and the rod despite such an accident has occurred, there has been already developed a hydraulic piercing apparatus equipped with a reverse-blowing unit to give a backward blow to the rod (Japanese Patent No. 2613538). The piercing apparatus equipped with the reverse-blowing unit has been widely used for opening the iron runner port of a blast furnace, since it makes it possible to relatively easily withdraw the rod by actuating the reverse-blowing unit when the rod cannot be withdrawn. On the site of work of this kind, however, much limitation is imposed on the working space, and it has been urged to provide a more compact piercing apparatus. Besides, the above conventional piercing apparatus requires at least five thick hydraulic hoses for operating the piercing apparatus, i.e., a hydraulic hose for forward blowing, a hydraulic hose for reverse blowing, a hydraulic hose for forward rotation, a hydraulic hose for reverse rotation, and a return hydraulic hose for forward and reverse blows, resulting in a complex external structure and hindering the operability.
It is therefore a requirement of the present invention to provide a piercing apparatus which is compact in size and uses a decreased number of hoses as a result of improving the above-mentioned conventional forward/reverse blow-type piercing apparatus.
In order to solve the above assignment, the present invention employs the following constitution. That is, the piercing apparatus of the invention executes the piercing by moving, back and forth by using a feed unit, a drifter equipped with a forward-blowing unit, a reverse-blowing unit and a rotary unit; wherein
cylinders containing a cylindrical blowing piston are provided in front of, and at the back of, a drifter body maintaining a distance relative to each other;
a shank rod having, formed as a unitary structure, a blowing portion of a large diameter with blowing surfaces formed on the front and rear portions thereof and rod-like small-diameter portions protruding forward and backward beyond the blowing portion, is provided along the axial direction of the drifter body in a manner that the blowing portion is positioned between the front cylinder and rear cylinder and that the small-diameter portions on both sides are fitted to the cylindrical blowing pistons of the respective sides; and
valves are provided in the outer peripheral portions of the front and rear cylinders to supply hydraulic pressure into the cylinders.
The rotary unit can be constituted in a relatively compact size if a spline is formed in the outer peripheral portion of the blowing portion of the shank rod, and if a chuck that transmits the rotation, by being spline-fitted to the blowing portion, is rotated by the rotary unit provided on the outer peripheral portion of the drifter body.
Further, a pilot valve unit is provided on the outer peripheral portion of the drifter body to selectively change the hydraulic pressure for blowing over to the valve for forward blowing or over to the valve for reverse blowing, and is changed over by the hydraulic pressure supplied to the feed unit in a manner that the hydraulic pressure is supplied to the valve for forward blowing by the hydraulic pressure for moving the feed unit forward and that the hydraulic pressure is supplied to the valve for reverse blowing by the hydraulic pressure for moving the feed unit backward. Then, the forward blow and the reverse blow are automatically changed over depending upon the change-over of the feed.
It is desired that a pilot valve unit for selectively changing the hydraulic pressure for rotation, over to the valve for forward rotation or over to the valve for reverse rotation, is provided on the outer peripheral portion of the drifter body from the standpoint of shortening the conduits and decreasing the size.
In the above piercing apparatus, it is desired to install, in a heat-resistant box, a valve for changing over all or part of the hydraulic pressure supplied to the blowing unit, rotary unit and feed unit and a valve for controlling the flow rate and pressure, and to install a cooling unit for forcibly cooling the interior of the heat-resistant box by purging the air as means for cooling the heat-resistant box. With the valve unit being installed near a guide cell for moving the drifter, the valve system can be constituted in a compact size. Similarly, it is desired to install, in a similar heat-resistant box, a valve for changing over all or part of the hydraulic pressure supplied to the blowing unit, rotary unit, feeding unit and to the pilot valve that changes over the direction of the blowing unit and the rotary unit, as well as to install a control valve for controlling the flow rate and pressure.
It is further desired from the standpoint of compactly arranging the hydraulic conduits that a return hydraulic pressure from the forward-blowing unit and the reverse-blowing unit meet a return hydraulic pressure from the rotary unit and/or the feed unit through the valve unit, so that the return hydraulic pressure is returned to a fluid tank through a common hydraulic hose.